Fix multiple generate (#1722)

### What problem does this PR solve?

#1625 

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

graph/component/answer.py

@@ -59,8 +59,10 @@ class Answer(ComponentBase, ABC):
         stream = self.get_stream_input()
         if isinstance(stream, pd.DataFrame):
             res = stream
+            answer = ""
             for ii, row in stream.iterrows():
-                yield row.to_dict()
+                answer += row.to_dict()["content"]
+                yield {"content": answer}
         else:
             for st in stream():
                 res = st